Congenital dehiscence of the bony facial canal, relevant during middle ear surgery, occurs most commonly in which location?

• A Tympanic segment adjacent to the oval window ✓
• B Mastoid segment near the pyramidal eminence
• C Labyrinthine segment at the meatal foramen
• D Second genu at the level of the horizontal semi-circular canal

Explanation

The tympanic (horizontal) segment of the facial canal, particularly the part overlying the oval window, is the commonest site of congenital dehiscence, reported in roughly half of temporal bones in some series. Here the nerve may lie exposed or even herniate over the promontory, making it vulnerable during stapes surgery or cortical mastoidectomy. The labyrinthine segment is the narrowest portion of the canal but is not the usual site of dehiscence.

Reference: Dhingra's Diseases of Ear, Nose and Throat, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.